1. Field of the Invention
The present invention relates to an electric wave receiving apparatus to receive an electric wave including a time code.
2. Description of the Related Art
In recent years, it has become possible to form a high-accuracy filter circuit having a small mounting area and a narrow passing band of signals by a micro electro mechanical system (MEMS) technique. Accordingly, it becomes possible to configure an electric wave receiving circuit capable of selectively receiving the signals of a plurality of receiving channels by using a variable filter composed of a plurality of filter circuits having mutually different passing frequency bands arranged in parallel with one another to be used to switch the filter circuit through which a received signal passes.
Moreover, as a technique related to the present invention, Japanese Patent Application Laid-Open Publication No. 2005-79981 discloses a technique using an MEMS filter as an intermediate frequency (IF) filter in a superheterodyne system receiver.
Moreover, Japanese Patent Application Laid-Open Publication No. 2005-5847 discloses a technique of applying a band-pass filter passing only signals having specific frequency components by using a plurality of MEMS filters in a reception section of a communication instrument.
Moreover, Japanese Patent Application Laid-Open Publication No. Hei 05-121947 discloses the technique of selectively extracting a signal of a specific frequency by connecting a plurality of high-frequency filters in parallel at the subsequent stage of an antenna in a direct conversion system receiving circuit to transmit the extracted signal to a mixer.
There is a case of performing the processing of searching for a receiving channel through which a signal can be received by receiving the signals of a plurality of receiving channels, and switching the receiving channels, if it is impossible to know the receiving channel of a wireless signal.